A film cartridge typically includes a rigid housing, at least one spool rotatable in film winding and unwinding directions within the housing, and a film roll wound onto the spool. The film roll has a clock-springing tendency to urge the spool in the film unwinding direction. An anti-backup pawl and cooperating ratchet teeth may be arranged on the housing and the spool for the pawl to engage any one of the ratchet teeth to prevent the clock-springing tendency of the film roll from urging the spool in the film unwinding direction and for the pawl to be disengaged from successive ones of the ratchet teeth when the spool is rotated in the film winding direction to wind the film roll onto the spool. See, for example, prior art U.S. Pat. Nos. 3,276,714 issued Oct. 4, 1966, and No. 3,286,945 issued Nov. 22, 1966.
The anti-backup pawl is usually resilient or springy in order to allow successive ones of the ratchet teeth to bend the pawl out of engagement with the respective teeth when the spool is rotated in the film winding direction. Conversely, the pawl engages any one of the teeth at a locking angle that prevents the pawl from yielding to disengage from that tooth when an attempt is made to rotate the spool in the film unwinding direction.